Studio for acoustic purposes



July 2, 1929. J. P. MAXFIELD STUDIO FOR ACOUSTIC PURPOSES Filed DeC. l5,1923 n l n v l n l L ffy;

Patented July 2, 1929.

UNITED STATES PTENT OFFICE.

JOSEPH P. MAXFIELD, OF MAPLEWOOD, NEW JERSEY, ASSIGNOR T WESTERN ELEC-TRIO COMPANY, INCORPORATED, OF NEW YORK, N. Y., .A CORPORA'TION OF NEWYORK.

STUDIO FOR ACOUSTIC PURPOSES.

Application led' December 15, 1923. Serial No. 680,814.

This invention relates to studios used for acoustic purposes,particularly, studios for broadcasting or sound recording.

The object of the invention is to provide a studio in which sounds maybe recorded or broadcasted with substantially all the natural effectsthat an auditor listening directly to the sounds would receive.

ln accordance with the general features of the invention, a studio isprovided in which the walls are so damped 'that the time ofreverberation will be such that the sounds recorded or broadcasted willgive the same acoustic effect as a person would experience in listeningto the same sounds under conditions which they are generally produced.More specifically, the invention provides` a studio in which the wallsare damped by a hanging curtain or applying other damping material tothe walls damping them to a degree such that the reverberation will bebetween .5 of a second and 1.0 second as determined by Sabines methoddisclosed in Collected papers on acoustics by W. C. Sabine, HarvardUniversity Press-1922. The damping material is preferably disposed onthe walls of the studio so that there willy be no large parallelreflecting surfaces opposite each other and arranged so that the soundwaves cannot travel around the room and back to the pickup devicewithout striking a damping surface.

Experiments have shown that owing to the time of reverberation in astudio, there is produced upon the listener, a different acousticaleffect depending upon whether he hears the sound with both ears orindirectly through a single pick-up device as in the case of reproducingsounds from records or broadcasting.

Under the usual conditions of hearing, reverberation is always presentto some extent and for this reason the effect produced on a person in aroom damped so that there is no perceptible reverberation is notnatural.

When a person listens to music or speech in a room he naturally usesboth ears and is thereby enabled by his binaural sense to discriminatebetween the direct source and the reflections which constitutereverberation.

He thereby subconsciously minimizes the blurring effect of thereverberation.

On the other hand when a person listens to the same sounds through asingle pick-up device he no longer hears them binaurally and hence losesthis abilit to discriminate between the source and t e reverberationsand the sounds reproduced are displeasing. Since the usual recording andbroadcasting apparatus is not binaural it is therefore, necessary todecrease the time of reverberation, that is, to damp each sound so thatit will not hang over so long. If this is not done the reproduced soundsbecome unnatural and if the reverberation is much too large the soundswill be blurred. The more sensitive the pickup device to the weakersounds, the greater must be the damping,

It has been found, that by damping the walls of a studio so that thetime of reverberatlon'will be between .5 of a second and 1.() second, asdetermined by Prof. Sabines method, records made in a studio so dampedwill g1ve an effect which is as near true binaural hearing as it ispossible to obtain wlthout actual binaural hearing. To most llstenersthis appears as natural as binaural hearing.

In the drawing Fig. 1 is a plan view of a studio embodying theinvention.

F 1g. 2 is an elevation of the studio.

On side walls 3, 4, 5 and 6 of the studio are hung sound-absorbingmaterial, preferably heavy curtains 7, 8, 9 and 10, respectively,extending substantially from the ceiling 11 to the floor l2 althoughthis is not necessary. The curtains may be hun on horizontal poles orrods 13 by any suita le fasteners which may be slidable on the rods,whereby the curtains may be adjusted to cover any desired surface tocontrol the damping. In the arrangement shown only a portion of eachwall is damped but the damping is so distributed that no large parallelundamped surfaces will be directly opposite each other. Felt or anyother suitable damping material may be used in place of curtains andfixed in position if desired. The ceiling` 1l as shown is not damped;but the floor 12 is substantially covered with a heavy rug 17. Smallerrugs ma be used on the floor and damping material may also be used onthe ceiling if desired. 18 is a source of sound such as a piano, thesound from which may be picked up by a suitable transmitter 16 connectedin a system suitable for recording or broadcasting, such as the systemdisclosed in application Serial No. 566,981, tiled June 9, 1922, for J.P. Maxfield.

lVhat is claimed is:

1. An acoustic studio for the conversion of sound waves into other formsof energy suitable for sound reproduction having damping means arrangedso that the time of reverberation is between .5 of a second and 1.()second.

2. An acoustic studio for the conversion of sound waves into other formsof energy suitable for sound reproduction, the Walls damped to theextent that the time of reverberation lies between .5 of a second and1.0 second.

3. In a .studio for the conversion of sounds from said source into otherforms of energy suitable for reproduction, means whereby the walls maybe damped to render the time of reverberation to not more than 1.0second.

4. An acoustic studio, damping means applied to a portion of the Walls,the damped portion being in a staggered relation with the undampedportions of opposite walls.

5. In an acoustic studio, damping means covering portions of the wallsthereof, an undamped portion of one wall being approximately opposite adamped portion of the opposite wall, and means supporting said dampingmeans for movement parallel to the walls whereby the damped area may bevaried to give a time of reverberation between one-half of a second andone second.

6. In an acoustic studio having a source of sound waves, a detector forconverting intercepted sound Waves into electrical variations fortransmission to a distance, means for controlling the quality of thesound as detected by said detector, said means comprising a plurality ofsound absorbing draperies spaced at intervals around the Walls of thestudio so that the time of reverberation is between .5 of a second and 1second.

7. In an acoustic studio including a source of sound waves and adetector, damping means applied to the walls of the studio in spacedrelation whereby all reflected sound waves are intercepted at least onceby said damping means before reaching said detector.

8. The method of treating studios for broadcasting or recordingentertainments which consists in arranging damping material in and aboutthe studio so as to give a time of reverberation between one-half of asecond and one second.

9. The method of treating acoustic studios for broadcasting or recordingentertainments which consists in absorbing sound at intervalsI along thewalls of the studio to such an extent that the time of reverberation isbe tween one-half of a second and one second.

In witness whereof` I hereunto subscribe my name this 14 day ofDecember, A. D., 1923.

JOSEPH P. MAXFIELD.

